This invention relates generally to filters or strainers, and more particularly to strainers used for filtering fluid upstream of a pump.
It is well known to provide a pump, such as a fuel pump within a fuel tank, with a filter or strainer upstream of the pump to inhibit contaminants or debris from entering the pump. It is also known to construct strainers having an outer layer of material, such as nylon, defining an inner cavity wherein anti-collapsing features are disposed to prevent the filter material from collapsing on itself. During operation, an inlet of the pump draws liquid, such as fuel within a fuel tank, through the strainer and into the pump. Desirably, the fuel is drawn into the pump without interruption, such as that which can occur by the introduction of vapor into the pump. If vapor does enter the pump, a condition known as xe2x80x9cvapor lockxe2x80x9d can result. Vapor lock typically results in problems downstream of the pump, such as engine sputter or stall.
Vapor lock is more likely to occur during certain conditions of operation, such as during turning of a vehicle or during low fuel conditions. To assist in inhibiting vapor from being drawn into the pump during these conditions, strainers are commonly constructed to provide a capillary seal when wet but not immersed in liquid fuel to prevent or at least inhibit the passage of fuel vapor therethrough. The capillary seal is generated at least in part by the surface tension of the fuel throughout the outer layer of the wetted filter material. The capillary seal typically provides for the drawing of fuel instead of drawing vapor through other portions of the filter in contact with liquid fuel and not through those portions of the filter not immersed in liquid fuel. However, if the capillary seal is broken or overcome by a pressure differential across the filter, fuel vapor can be drawn into the filter and ultimately into the pump.
The use of anti-collapsing features can increase the likelihood that fuel vapor will be drawn into the pump because they typically create a tortious path through which the fuel must flow in order to get to the inlet of the fuel pump. This makes it more difficult to draw fuel from a portion of the strainer that is remote from the inlet of the fuel pump. This in turn can increase the pressure differential across portions of the strainer adjacent the inlet of the pump. If these portions of the strainer are exposed to vapor, then vapor may be drawn into the pump due to the increased pressure differential. As such, vapor lock is more likely to result if the fuel is inhibited or restricted from flowing directly to the inlet of the fuel pump.
A strainer for a fuel pump enables substantially unrestricted flow of fuel into the inlet of the fuel pump, while inhibiting vapor from entering the fuel pump. The strainer has at least one layer of permeable material forming a substantially enclosed cavity having at least one wall. A body is disposed at least in part in the cavity such that the body has a surface adjacent to at least a portion of the wall. The body has at least one tubular portion arranged for fluid communication with the inlet of the fuel pump. The tubular portion provides a fuel flow path to the fuel pump inlet that has reduced or minimal resistance.
Objects, features and advantages of this invention include providing a strainer for a fuel pump that inhibits collapsing of walls of the strainer, inhibits fuel vapor or air from flowing into the fuel pump, provides for generally unrestricted flow of liquid fuel into the fuel pump, reduces the potential sources for vapor entry into the fuel pump, facilitates drawing liquid fuel to the fuel pump from remote portions of the filter, increases the efficiency of the fuel pump, provides a more consistent flow of liquid fuel from the fuel pump, is compact, rugged, durable, of relatively simple design and economical manufacture and assembly, and has a long useful life in service.